Process and apparatus for removing protruding fibers from spun thermoplastic linear polymer yarns



Feb. 27, 1962 F; CQPRICE 3,022,564

PROCESS AND APPARATUS FOR REMOVING PROTRUDING FIBERS FROM SPUN THERMOPLASTIC LINEAR POLYMER YARNS Filed June 2, 1958 WVWVVVVWNWWV FIG.3 -FIG.2 FIG.4

FEEDER/CK CHAWLES Pew:

WMO MML /7 TTOK/VA'YS nite States This invention relates to a textile process, more particularly it relates to a process for singeing yarns spun from synthetic thermoplastic linear polymer fibres such as the polyester fibres and nylon.

Many processes are known in the art for the singeing treatment of spun yarns in which fibres protruding from the main body of a yarn are burnt ed by passing the yarn through a fiarne or an electrically heated groove, at speed. Numerous apparatus for carrying out this process are known and are described, for example, in British Patent 696,395, which comprises a groove through which the yarn is passed and singed by an electrically heated resistance which lines the bottom and sides of the groove in the form of a wire which may be bent into zig-zag bends, with the plane of the bends then further bent round to form a U so that it constitutes a channel which is introduced into the groove.

Another apparatus for singeing yarn consists of a wire supported in a heat resistant channel of circular cross section, to prevent distortion of the wire which is bent into a coil or similar shape of circular plane section in end view.

When yarns spun from synthetic thermoplastic fibres are treated by the conventional singeing apparatus it is very much more difiicult to remove the protruding fibre ends, than in the case of non-thermoplastic fibres such as cotton.

Difficulty arises because the thermoplastic fibres are not amenable to the usual gas or singeing treatment. Heat entering the fibres at their tips causes them to contract towards the body of the yarn and eventually to melt, to form beads on the surface of the yarn. Unlike cotton, the protruding fibres do not char and they cannot be brushed ofi or fall off in the usual way. Furthermore, the large beads formed by the conventional gas or singeing process have a higher dye uptake than remaining fibres in the yarn. Fabrics woven or knitted from such yarns exhibit spots of a darker shade where the contracted fibres and beads are situated. Fabrics made from such yarns also have a harsh handle.

According to our invention we provide a process for removing protruding fibres from a spun yarn comprising synthetic thermoplastic linear polymer fibres, such as polyethylene tcrephthalate and nylon fibres, comprising passing the yarn at speed through a singeing device, wherein said protruding fibres strike a number of hot, substantially fiat surfaces disposed in succession along the yarn path, on both sides thereof and at approximately right angles threto, so that the fibres are severed by the edges of said hot surfaces. Preferably the effective parts of the edges of the hot surfaces are straight. It is further preferred tha. said surfaces should be such that the yarn passes along a V-shaped groove formed by said surfaces. The moving yarn may be threaded into the open ends of the V-shaped groove by tensioning between suitably disposed guides at either end of the device where it finds its own level by moving towards the base of the V-shaped groove.

Our invention also comprises a singeing device made up of a number of flat surfaces positioned in line so that strip, before bending it into the zi -zag shape.

3,022,564 Patented Feb. 27, 1962.

a V-shaped groove is formed, and means for heating said surfaces.

The surfaces are conveniently made from a thin metal electrical resistance strip which may either be bent into Zig-zag shape, or into which suitable notches are cut or punched at intervals. in one form of our invention the metal strip is bent into a substantially symmetrical zig-zag and the crests of the zig-zag displaced sideways, the first to the left and next to the right and so on, so that a V- shaped groove is formed between the displaced crests. The angle contained by the V-shaped groove should preferably be less than The device may be heated by electric current passed through the strip.

Instead of displacing the crests of the zig-zag shaped thin strip sideways, the VShflPBd groove may be formed by cutting V-shaped notches in a line into the crests of the zig-zag bent strip in which the crests are substantially in a straight line in end view. Preferably the notches should be cut, or they may be formed by punching, at intervals in the middle or at the sides of the strip.

It will be appreciated that when the notches are made by punching, this should preferably be done, on the fiat Vhen the notches are to appear in successive crests of the zigzag substantially rhomboid or hexagonal holes are suitable, which form a number of pairs of V-shaped grooves, in the crests when the strip is subsequently bent into zigzag shape. if it is desired to have the V-shaped grooves on one or both sides of the zigzag, V-shaped notches may be punched or cut at suitable intervals into the edges along the sides of the fiat strip. Care must be taken on bending the strip into zig-zag shape, to ensure that the cut out notches should form a substantially straight line, to facilitate threading and the subsequent passage of the yarn. The punched or cut notches should be free from burrs and rough edges.

An electric current is passed through the strip in order to heat it to the required temperature. When the strip has been provided with notches or V-shaped cut-outs the greatest heat is developed in those parts of the conducting metal surrounding the notches.

The metal strip may be bent into the zig-zag shape to give, e.g. an amplitude of about 1 cm. from crest to trough of the zigzag, and about 7 crests in 15 cm. of the linear strip. The V-shaped grooves are formed by bending successive crests sideways or by cut-outs, as previously described.

The spacing of the V-shaped surfaces is not critical and 10 surfaces spaced over a distance of 10 cm. have given good results. Using yarn speeds e.g. of about 250 metres per minute we have found that the yarn should pass at least 3 V-shaped surfaces. The distance between the first and last edged surface and the positioning of the yarn should be such that the yarn has time to expose all the fibres protruding from its circumference to the V-shaped surfaces. The yarns are passed in close proximity to the surfaces heated to an appropriate temperature, or preferably make scraping contact with them. The melting temperature of the protruding fibres, the yarn speed and the temperature of the hot surfaces are interconnected variables which may be determined by experiment. Temperatures of at least 500 C. and well above the melting temperature of the fibres are required. It will be appreciated that the edged surfaces should be thin to help the severing of the protruding fibres from the body of the yarn when the protruding fibre ends strike and get caught by the flat hot edged surfaces.

A number of metal resistant strips are commercially available in a range of width and thicknesses. The strips should be at least 1.5 mm. wide and sufiiciently thin to provide scraping edges. We have found that strips about 2 mm. wide and 0.2 mm. thick having a resistance of r 3 about 3 ohms per cm. have the required characteristic and mechanical rigidity when fabricated as described for use in our process. When a low voltage current of about 10l8 amps. and 5-12 volts is passed through such a thin metal strip temperatures of about 1200 C. can be reached.

The yarn may be rotated whilst passing between guides, positioned at either end of the singeing device, but we have found that no special means are necessary for rotating the yarn, as sufiicient rotation occurs when a spun twisted yarn is under tension whilst passing between the guides to close to or in scraping contact with the edged surfaces. lt will be appreciated that the yarn should make at least one complete turn whilst advancing between the first and last V-shaped surface in order to expose all the protruding fibres to the hot edged surfaces.

Protruding fibre ends, on striking the flat metal strip are stuck, melt andare severed from the main body of the yarn by the relatively sharp edges of the hot metal, as the yarn moves on, and before the protruding fibre ends have time to contract back into the yarn. The stuck fibre ends are severed and melt and are subsequently burnt by the hot metal.

Whilst the edged surfaces of a thin metal strip give the desired result when heated to the appropriate temperature, a wire of round cross section'bent into zig-zag shape and heated to the same temperature has not given the improvement. It is believed that the protruding thermoplastic fibres tends to be flattened and are not severed by the hot wire and are therefore not removed from the yarn; instead they contract into beads which remain on the yarn.

It is a well known phenomenon that when yarns of artificial fibres, for example, polyester or nylon fibres, are twisted there is a strong tendency for them to untwist unless they are subjected to some form of restraint. This tendency to untwist is measured quantitively by a factor known as the snarling twist and the method of measurement is described in British Standards Institution Handj book No. 11, 1956, page 90.

We have found that when twisted yarns of polyester fibres are treated according to the process of the invention the yarn so treated has a very much reduced tendency to untwist or snarl. A 2/ 80s cotton type spun yarn of polyethylene terephthalate with a doubling twist of 33 turns per inch had its snarling twist reduced from 5 turns per inch to 1 turn per inch after being treated according to the process of our invention. 'It is believed that the. snarling twist in the yarn is reduced by the heat radiating from the device to the body of the yarn so that the twist in the yarn becomes set. V

The following examples and the attached drawings illus trate but do not limit our invention.

FIG. 1 is a diagrammatic side view of a metal resistanc strip, bent into zig-zag shape.

Example 1 Polyethyleneterephthalate cotton spun yarns comprising 1 /2" polyethylene terephthalate crimped staple fibres having numerous fibres protruding in all directions from the main body of'the yarn, is passed at speeds of 200350 metres per minute through a straight line of V-shaped grooves formed by opposing successive edges of 'a zig-zag bent metal resistance strip Brightray (registered trademark) 2 mm. wide and 0.2 mm. thick, having a resistance of about 3 ohms per meter. A The strip is heated to betweenSOO-IOOG Crby a'current supplied from the mains through a 25 volt transformer and a second adjustable transformer. The voltage is kept between 8 and 12 volts. The strip is bent into a zig-zag line as shown diagrammatically in FIGS. 1 and 2, so that about 7 crests of 1 cm. amplitude are formed in 14 cm. of the flat strip. The crests of the strip are displaced sideways, the first to the right the next to the left and so on, until successive opposing edges of the whole row of the zig-zag bent strip form a V-shaped groove of about 45 angle in end view as shown diagrammatically in FIG. 3. 'The strip is supported in a groove /1" wide by /2" deep milled in a 6" x /1 x A block of St. Daniel v(registered trademark) cement/ asbestos block. The ends of the strip are screwed to stainless steel terminal connectors mounted in the block.

Threading of the spun yarn is quite simply accomplished by tensioning the running yarn between adjustable guides positioned on either end beyond the metal strip, so that the main body of the yarn is about 1mm. from the bottom of the V-shaped groove. Polyethylene terephthalate staple fibres of 1 /2 to 6 denier, spun into yarns of cotton counts from 10s to60s have been processed satisfactorily with the device, minor adjustments of the guides being made to obtain the correct positioning of the main body of the yarn in the V-shaped groove, or whilst making scraping contact with the edges of the strip. By'applying a slight tension as the yarn is passed between the guides, a slight rotation of the yarn occurs so that the protruding ends are removed when contacting successive edged surfaces of the hot metal strip When leaving the device the yarn is smooth and substantially free from protruding polyethylene terephthalate fibres.

Example 2 The process of Example 1 is repeated using a metal strip which is bent into zig-Zag shape as in Example 1, but the crests of which are left in one line as shown in E63. 1 and 2. V-shaped notches of about 45 angle, 3 mm. deep are cut into the line of crests in the strip. The bent metal strip is mounted on a ceramic support so that the double notches cut into the crests of the zig-zag bent strip form a straight line of V-shaped grooves in end view, as shown diagrammatically in PEG. 4. A current supplied from the mains through transformers as in Example 1 is adjusted so that the metal strip in the crests surrounding the notches glows with bright orangecolour,

which corresponds to a temperature of about 1160 C.

It is of notable advantage that the metal strip gets hottest around the cut out notches, where the heat is most effective for singeing the yarn.

Adjustable guides are positioned beyond the ends of the strip so that a yarn, when tensioned between the guides, is about 1 mmjfrom thebottom of the V-shaped notches, cut in the crests of the bent metal strip. Polyethylene terephthalate filaments are passed through at speeds as in Example 1, when a smooth yarn substantially free from protruding fibre ends is obtained.

Instead of using one long strip to give a large number of edged surfaces, a number of short strips, end to end may be used in one line for the same purpose.

If desired a number of identical strips, suitably shaped, may beused simultaneously for the singeing of a number of yarns, running side by side. The ends of the strips may be connected in parallel or in series, with single means for controlling the temperature in all the strips.

The yarns treated according to our invention are much superior to spun synthetic thermoplastic yarn singed on conventional machinery using direct open flames or any of the other known electrically heated singeing devices. Our process is also suitable for treating blends of synthetic thermoplastic fibres with natural fibres or regenerated cellulose fibres.

Fabrics made from yarn treated accroding to our invention are much smoother in appearance, and in wear show a reduced tendency to form pills, i.e. small balls of fibres on the surface of the fabric. We have also found that our singed yarns facilitate weaving, because there are no protruding fibres which get caught and which interfere with adjacent yarns.

We have found that cotton type shitting fabrics woven from 1/40s cotton spun polyethylene terephthalate fibres singed as in Example 1 showed on average only 5 pills per square inch, when subjected to a comparative pilling test, whereas a fabric woven from unsinged yarn showed on average 119 pills per square inch, and a fabric woven from gas singed yarn showed on average 39 pills per square inch.

Moreover the fabric containing the gas singed yarn showed dark spots when dyed which corresponded to blobs formed by fibres which had retracted during the gas singeing treatment. Fabrics containing yarns singed according to our process when dyed did not show dark spots.

What I claim is:

1.A process for removing protruding fibres from a spun yarn comprising synthetic thermoplastic linear polymer with a singeing device, having a plurality of hot substantially flat surfaces disposed in spaced succession along the yarn path on both sides thereof with the planes of said surfaces at substantially right angles to said yarn path and the edges thereof adjacent said yarn path, which comprises passing said yarn through said device sulficiently close to said surfaces that the protruding fibres strike said surfaces as the yarn passes along said yarn path through the singeing device, and maintaining said surfaces at a substantially uniform temperature above 500 C. whereby the protruding fibres are severed at the edges of said fiat surfaces.

2. A process according to claim 1 wherein the effective part of the edges of said hot surfaces are straight.

3. The process according to claim 1 wherein said surfaces are disposed in spaced succession along the yarn path so that the yarn passes along a V-shaped groove in end view, formed by said surfaces.

4. A process according to claim 1 wherein the surfaces are disposed in spaced succession along the yarn path, so that the yarn passes along a V-shaped groove in end view, formed by said surfaces and wherein the yarn is threaded into the open ends of the V-shaped groove by tensioning between suitably disposed guides at either end of the device, where it finds its own level by moving towards the base of the V-shaped groove.

5. A process as set forth in claim 1 including maintaining said yarn under tension between guides while passing it through said singeing device, said guides being positioned at the ends of said singeing device.

6. Apparatus for singeing removal of protruding fibers from spun yarn composed of synthetic thermoplastic fibers, which comprises a thin, generally flat, electrical resistant metal strip at least 1.5 mm. wide and bent in substantially uniform zig-zag configuration, thin, sharp, scraping and singeing edges on said strip between bends in said zig-zag configuration, adjacent pairs of said scraping and singeing edges intersecting each other at acute angles to form a series of V-shaped notches, said notches being spaced successively from each other on, and generally transverse in their own plane, to a predetermined path along the length of said zig-zag configuration yarn handling means for delivering said yarn at a uniform, rcgulatable high speed along said path and through said notches, and adapted to maintain said yarn in singeing contact with said edges for removal of said protruding fibers, and electrode means for passing an electrical current through said resistance members as the sole means for controllably heating the same and maintaining a temperature thereof above 500 C.

7. The apparatus of claim 6 wherein said strip is bent into said zig-zag configuration in which the crests of the zig-zag are displaced sideways, alternately to the left and to the right, of said predetermined path so that said V-shaped notches are formed between the displaced crests.

8. The apparatus of claim 6 wherein said strip has portions punched out therefrom at spaced intervals along the len th of the strip, the holes thereby formed having straight edges, said zig-zag configuration being arranged so that the holes are respectively in line in the crests of said zig-zag configuration and said straight edges are arranged as said thin, sharp, scraping and singeing edges, forming V-shaped notches in the zig-zag configuration, in end view.

9. The apparatus of claim 6 wherein said strip is a thin, metal electrical resistance strip about 2 mm. wide and 0.2 mm. thick, with a resistance of about 3 ohms per centimeter.

10. An apparatus comprising a plurality of thin, generally fiat, electrical resistant metal strips arranged as set forth in claim 6 and generally parallel and side-byside each other for the singeing removal of protruding fibers from a plurality of said spun yarns with means for electrically connecting the ends of the strips and single means for controlling the temperature in all the strips.

11. Process for singeing and complete removal of protruding fibers from spun yarn composed of synthetic thermoplastic fibers, which process comprises the steps of passing said yarn under tension at a high speed along a predetermined path and intermittently, and briefly and rapidly, scrapingly contacting said yarn with a plurality of thin, sharp scraping and singeing edges of a generally flat, electrical resistance-heated metal strip, softening said protruding fibers on contact with said edges and thereby sticking them to said edges while simultaneously severing the same from the main body of said yarn and subsequently melting the removed fibers on the fiat surface of said strip, said predetermined path being along an array of V-shaped notches spaced respectively from each other and formed by said scraping and singeing edges, said edges being maintained at a controllable temperature of 560 C. 7

References Cited in the file of this patent UNITED STATES PATENTS 696,395 Great Britain Aug. 26, 1953 

1. A PROCESS FOR REMOVING PROTRUDING FIBRES FROM A SPUN YARN COMPRISING SYNTHETIC THERMOPLASTIC LINEAR POLYMER WITH A SINGEING DEVICE, HAVING A PLURALITY OF HOT SUBSTANTIALLY FLAT SURFACES DISPOSED IN SPACED SUCCESSION ALONG THE YARN PATH ON BOTH SIDES THEREOF WITH THE PLANES OF SAID SURFACES AT SUBSTANTIALLY RIGHT ANGLES TO SAID YARN PATH AND THE EDGES THEREOF ADJACENT SAID YARN PATH, WHICH COMPRISES PASSING SAID YARN THROUGH SAID DEVICE SUFICIENTLY CLOSE TO SAID SURFACES THAT THE PROTRUDING FIBRES STRIKE SAID SURFACES AS THE YARN PASSES ALONG SAID YARN PATH THROUGH THE SINGEING DEVICE, AND MAINTAINING SAID SURFACES AT A SUBSTANTIALLY UNIFORM TEMPERATURE ABOVE 500*C. WHEREBY THE PROTRUDING FIBRES ARE SEVERED AT THE EDGES OF SAID FLAT SURFACES. 